1. Field of the Invention
The present invention relates generally to an image switching apparatus for switching and outputting a video signal from inputted video signals of a plurality of channels and which is able to perform effects on a video signal when video signals are switched, and particularly to an image switching apparatus by which circuits can be efficiently used without waste in response to a use and a method of controlling an image processing unit of such an image switching apparatus.
2. Description of the Related Art
So far an image switching apparatus (switcher) is available as one of professional apparatus for use in editing pictures in a television broadcast or the like. The image switching apparatus is able to switch and output a video signal from inputted video signals (video signals from a video camera, a VCR (video cassette recorder) and etc.) of a plurality of channels and which is also able to perform a suitable effect such as wipe on a video signal when video signals are switched. An outputted video signal from the image switching apparatus is supplied to television program transmission equipment, a video recording apparatus, a monitor and the like.
In video edit work, it is customary that a video signal of only one channel should be generated or that video signals of a plurality of channels should be generated at the same time. Concurrently therewith, it is requested that the image switching apparatus should have functions that can be used in a variety of purposes.
FIG. 1 of the accompanying drawings is a schematic block diagram showing an example of a related-art image switching apparatus having such functions. As shown in FIG. 1, this image switching apparatus includes a plurality of image processing units 51 (51a to 51d) in which an outputted video signal from one image processing unit 51 is inputted again to other image processing unit 51 as an inputted video signal. Each image processing unit 51 includes an input selection unit 52. The input selection unit 52 includes a matrix-like selection switch group by which input lines 53a to 53j are connected to any of input buses 54a to 54c and it is able to select video signals of one channel each by the input buses 54a to 54c. The video signal selected by the input selection unit 52 is supplied to a synthesis processing unit 55, in which it is applied with effects such as wipe and mix and outputted from an output terminal Output and also inputted again to other image processing unit 51 from input lines 53g to 53j (see Cited Patent Reference 1, for example).
This image switching apparatus selects the input lines 53g to 53j (output video signals of other image processing unit 51) by the input selection unit 52 of the image processing unit 51 and becomes able to generate a video signal of one channel, which has been applied with effects of a plurality of stages, (becomes able to output the video signal of one channel from the output terminal Output of the image processing unit 51 of the final stage) in the state in which the image processing units 51 of a plurality of stages are connected in series.
Also, this image switching apparatus does not use the input lines 53g to 53j by the input selection unit 52 of the image processing unit 51 and hence this image switching apparatus becomes able to generate video signals of a plurality of channels which has been applied with effects (this image switching apparatus becomes able to generate the video signal of one channel from the output terminal Output of the image processing unit 51 of the final stage).
Cited Patent Reference 1: Official Gazette of Japanese laid-open patent application No. 2004-153486 (paragraph Nos. 0048 to 0054 and FIG. 2)
Professional image switching apparatus are very expensive and it is unavoidable that their prices are considerably increased when the number of circuits and the channel between the circuits are increased. For this reason, it is requested not only that the image switching apparatus should have functions which can be used in a variety of purposes and but also that the price of the image switching apparatus should be decreased by decreasing the number of circuits.
However, in the image switching apparatus described in the above-described Cited Patent Reference 1, when video signals, on which simple effect was performed, of channels lesser than the number of the image processing units 51 (for example, video signals of one channel or two channels) are generated, only a part of the image processing units 51 is used and the remaining image processing units 51 are not used at all. As described above, the image processing units 51, which are not used depending on a variety of purposes, should be provided and hence it is difficult to decrease the price of the image switching apparatus.